Hello Tiranoluggage
Oh, you are going to ride two of the most picturesque train lines in Switzerland. On the Bernina line, try to find a seat on the left hand side in travel direction, for better views.
For the moment, the prebooking only works for stations in Switzerland. However, there is no need to prebook the station-to-station luggage transfer service in advance; you are welcome to show up at the station at Tirano and order it on-site while dropping your luggage.
The only condition: you must be in the possession of the ticket for Interlaken when ordering the luggage transfer service.
Kind regards,
Roland